The minimum listed temperature for the various strains on the Wyeast and White Labs websites are generally about 5 degrees higher than what I have found to be the actual minimum. With most American and British-style ales there is little to no downside to fermenting cooler than the listed minumim (and frequently there is a major benefit to fermenting cool). I keep my fermentation chamber at 58 for most ales, so as to obtain a fermentation temperature of around 62-64F. If I am fermenting with WLP001/Wyeast 1056/US-05 (all essentially the same strain), or with certain other strains (Pacman and Wyeast 1007, in particular like it very cold), I will set my chamber to 54F, so as to obtain a fermentation temperature of 58-60F. The issue is when your ambient temperature is higher than 65F or so, then you are likely to be fermenting too warm for most styles, but Belgian ales are happily made with warmer fermentations. In particular, Wyeast 3864 Canadian/Belgian is EXCELLENT at producing tasty Belgian-style beers when ambient is very warm (70-75F), as are the various Saison strains.